A known apparatus for making thermoplastic monofilaments by spinning has at least one spinneret suppliable with a thermoplastic material with at least one spinning plate and a plurality of spinning holes for the individual monofilaments. The thermoplastic material is forced through the spinning holes by at least one spinning pump. The express form of a spinning hole comprises a passage through the spinning plate.
In practice each spinning hole is a spinning passage in the spinning plate. Thus the spinning holes are a group of passages. The spinning plate has up to a hundred and twenty spinning passages. Generally a plurality of spinning pumps are provided which are controlled by a single controller or a single pump can feed a number of spinnerets. The diameter of the product monofilament is measured from time to time in a laboratory and the controller is used by an operator to change the value of the diameter of the output according to the measured diameter. Thus the control loop is completed by an operator and the laboratory technicians doing the measurement. In such a control process a considerable degree of subjective judgement goes into the measurements made by the individuals involved. Furthermore a considerable dead time occurs. The errors due to that and the variations in diameter of the monofilament are considerable.